• 한국산업보건학회지
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• 제4권1호
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• pp.81-95
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• 1994

This study was performed in a diatomite factory where silicosis had been found at October, 1993. The major objectives were to evaluate worker exposure to diatomaceous earth and to present engineering control methods for workplace management. Total and respirable dust of diatomaceous earth were measured. Size distribution of dust was analyzed by applying the multiple diffraction method. Also crystalline silica in respirable dust samples was analyzed qualitatively by X-ray diffraction. The suitable Local Exhaust Ventilation systems for that factory were recommended. The results were as follows. The airborne total and respirable dust concentrations by exposure groups showed approximate normal distribution. The means of total dust exposures at flour maufacturing, fire brick grinding and packaging, ceramic raws packaging processes exceeded Korean and ACGIH standards, $10mg/m^3$. The means of total and respirable dust concentrations to high exposure groups were 6.8 and 3.9 times higher than those of low expousre groups, respectively. The size distribution of diatomaceous earth dust was lognormal with a median diameter of $7.07{\mu}m$(range, $0.10-60.0{\mu}m$) and with a geometric standard deviation of 1.43. The crystalline silica in respirable dust samples was identified to quartz and cristobalite and/or tridymite. Above results suggest that engineering controls and periodic environmental and medical surveillances will be important for preventing silicosis in the diatomite factory.

• Safety and Health at Work
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• 제10권4호
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• pp.518-526
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• 2019

Background: Additive manufacturing (AM) is a rapidly expanding new technology involving challenges to occupational health. Here, metal exposure in an AM facility with large-scale metallic component production was investigated during two consecutive years with preventive actions in between. Methods: Gravimetric analyzes measured airborne particle concentrations, and filters were analyzed for metal content. In addition, concentrations of airborne particles <300 nm were investigated. Particles from recycled powder were characterized. Biomonitoring of urine and dermal contamination among AM operators, office personnel, and welders was performed. Results: Total and inhalable dust levels were almost all below occupational exposure limits, but inductively coupled plasma mass spectrometry showed that AM operators had a significant increase in cobalt exposure compared with welders. Airborne particle concentrations (<300 nm) showed transient peaks in the AM facility but were lower than those of the welding facility. Particle characterization of recycled powder showed fragmentation and condensates enriched in volatile metals. Biomonitoring showed a nonsignificant increase in the level of metals in urine in AM operators. Dermal cobalt and a trend for increasing urine metals during Workweek Year 1, but not in Year 2, indicated reduced exposure after preventive actions. Conclusion: Gravimetric analyses showed low total and inhalable dust exposure in AM operators. However, transient emission of smaller particles constitutes exposure risks. Preventive actions implemented by the company reduced the workers' metal exposure despite unchanged emissions of particles, indicating a need for careful design and regulation of the AM environments. It also emphasizes the need for relevant exposure markers and biomonitoring of health risks.

• 한국산업보건학회지
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• 제24권4호
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• pp.462-470
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• 2014

Objectives: The purpose of this study was to evaluate quartz concentrations in airborne respirable dust and particle size-related quartz concentrations. Methods: Respirable dust samples were collected using a 10 mm Dorr-Oliver nylon cyclone equipped with a 37 mm, $5{\mu}m$ pore size PVC filter. Dust samples were collected with a Marple's personal cascade impactor from stone grinding operations in five stone-related business located in the Gyeongsangbuk-do area. Results: The geometric mean of quartz concentration in the respirable dust was $0.170mg/m^3$, and the rate of exceeding the Korean Occupational Exposure Limit(KOEL) was 93.3%. The quartz concentration by particle size shows that it was the highest($0.115mg/m^3$) in stage 5($3.50-6.00{\mu}m$), which corresponds with the size of respirable particle. The smaller the particle sizes were, the higher quartz the content became. The mass fractions of inhalable, thoracic, and respirable dust were 72.1%, 36.0%, and 14.4%. Conclusions: The rate of the quartz concentration in respirable dust from stone grinding operations exceeding the American Conference of Governmental Industrial Hygienists Threshold Limit Values was 100%, which means proper work environmental management is required through regular working environmental measurements. Given that the stone grinding operations had a higher small size dust concentrations, there is a need to reduce respirable dust, such as through wet operation and local exhaust ventilation.

• 한국산업보건학회지
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• 제5권2호
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• pp.212-225
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• 1995

This study was performed in a diatomite factory located at Pohang City, Kyeongsangbuk-Do. The major objectives were to evaluate sampling and analytical methods of diatomaceous earth dust. Concentrations of total and respirable diatomaceous earth dust were measured. Size distribution of dust was analyzed by a personal cascade impactor and the particle size analyzer which is an application of multiple diffraction method. Also crystalline silica in respirable and total dust samples was analyzed quantitatively by X-ray diffraction and Fourie Transform Infrared Spectroscopy(FTIR). The results were as follows: The airborne total and respirable dust concentrations, particle size distribution, and cristalline silica(quartz) concentrations showed approximately a log-normal distribution. The means of totaldust concentrations at flour maufacturing, fire brick grinding and packaging processes exceeded the Korean and American Conference of Governmental Industrial Hygienists standards, $10mg/m^3$. The size distribution of diatomaceous earth dust was log-normal and identified as the rspirable particle mass and thoracic particle mass. The crystalline silica in respirable and total dust samples was identified to quartz and contained about 10 % in those samples. Finally, it is necessary to study the applicability of multiple diffraction for particle size distribution to compare the ACGIH's size selective sampling with other materials containing crystalline silica. Also, advanced quantitative study to X-ray diffraction and FTIR methods shoud be carried out 10 verify general and specific characteristics for respirable crystalline silica.

• 한국환경보건학회지
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• 제32권4호
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• pp.254-261
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• 2006

In activity areas of subway workers and passengers in Seoul metropolitan subway lines 1-4, mein concentrations of airborne bacteria were relatively higher in workers' bedroom and station precinct whereas concentrations of particulate matters, $PM_{10}$ and $PM_{2.5}$, were relatively higher in platform, inside train and driver's seat as compared with other activity areas. This result indicates that little correlation between airborne bacteria and particulate matters was found, which assumed that most airborne particulate matters distributed in subway consisted of mainly inorganic dust like a metal particles. Mean concentrations of $PM_{10}$ and $PM_{2.5}$ in station precinct and platform exceeded the threshold limit value ($PM_{10}:150{\mu}g/m^3,\;PM_{2.5}:65{\mu}g/m^3$) but those in station office and ticket office were below it. The genera identified in all the activity areas of subway over 5% detection rate were Staphylococcus, Micrococcus, Bacillus and Corynebacterium, of which Staphylococcus and Micrococcus covered over 50% of total airborne bacteria and were considered as predominant genera distributed in subway.

• 한국축산식품학회지
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• 제28권5호
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• pp.623-628
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• 2008

This study was undertaken to determine the concentrations of airborne bacteria, fungi, particles, and endotoxin in swine and chicken houses. Six swine buildings and seven chicken houses were randomly selected in southern Gyonggi Province, South Korea. The geometric mean concentrations of airborne bacteria in swine and chicken houses were $2.7{\times}10^5\;CFU/m^3$ and $5.6{\times}10^7\;CFU/m^3$, respectively. The airborne bacteria concentrations in chicken houses were significantly higher than those of swine houses (p<0.05). The geometric mean concentration of airborne fungi in swine houses was $4.9{\times}10^3\;CFU/m^3$, which was higher than the value of $2.1{\times}10^3\;CFU/m^3$ found in chicken houses. The mean concentrations of airborne particles and endotoxin in swine houses were $3.48\;mg/m^3$ and $943.1\;EU/m^3$, and they were $15.43\;mg/m^3$ and $1,430.5\;EU/m^3$ in chicken houses, respectively. A significant difference between swine and chicken houses was found for total dust (p<0.05), but not for endotoxin. In this study, the concentrations of endotoxin in both swine and chicken houses as well as particles in chicken houses were high, and in about 50% of the samples exceeded the worker health safety levels of $614\;EU/m^3$ suggested in previous studies. These results may indicate a considerable respiratory hazard for workers in these environments.

• 한국산업보건학회지
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• 제24권1호
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• pp.65-73
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• 2014

Objectives: The purposes of this study are to investigate workers' exposures to respirable particles generated in taconite mines and to compare two metric methods for mass concentrations using direct-reading instruments. Methods: Air monitorings were conducted at six mines where subjects have been exposed primarily to particulate matters in crushing, concentrating, and pelletizing processes. Air samples were collected during 4 hours of the entire work shift for similarly exposure groups(SEGs) of nine jobs(N=37). Following instruments were employed to evaluate the workplace: a nanoparticle aerosol monitor(particle size range; 10-1000 nm, unit: ${\mu}m^2/cc$, Model 9000, TSI Inc.); DustTrak air monitors($PM_{10}$, $PM_{2.5}$, unit: $mg/m^3$, Model 8520, TSI Inc.); a condensation particle counter(size range; 20-1000 nm, unit: #/cc, P-Trak 8525, TSI Inc.); and an optical particle counter(particle number by size range $0.3-25{\mu}m$, unit: #/cc, Aerotrak 9306, TSI Inc.). Results: The highest airborne concentration among SEGs was for furnace operator followed by pelletizing maintenance workers in number of particle and surface area, but not in mass concentrations. The geometric means of $PM_{2.5}$ by the DustTrak and the Ptrak/Aerotrak were $0.04{\mu}m$(GSD 2.52) and $0.07{\mu}m$(GSD 2.60), respectively. Also, the geometric means of RPM by the DustTrak and the Ptrak/Aerotrak were $0.16{\mu}m$(GSD 2.24) and $0.32{\mu}m$(GSD 3.24), respectively. The Pearson correlation coefficient for DustTrak $PM_{2.5}$ and Ptrak/Aerotrak $PM_{2.5}$ was 0.56, and that of DustTrak RPM and Ptrak/Aerotrak RPM was 0.65, indicating a moderate positive association between the two sampling methods. Surface area and number concentration were highly correlated($R^2$ = 0.80), while $PM_{2.5}$ and RPM were also statistically correlated each other($R^2$ = 0.79). Conclusions: The results suggest that it is possible to measure airborne particulates by mass concentrations or particle number concentrations using real-time instruments instead of using the DustTrak Aerosol monitor that monitor mass concentrations only.

• Asian Journal of Atmospheric Environment
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• 제10권3호
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• pp.162-167
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• 2016

This study was conducted in an industrial city (Bilaspur) representative of subtropical area in central India. In order to assess the metal deposition on plant, concentrations of six target metals (i.e., Fe, Mn, Pb, Cu, Cd, and Cr) in both plant leaf and dust (deposited on its surface) samples were measured from six different sites. Metal concentrations in dust samples were found on the order of Fe>Mn> Cr>Pb>Cu>Cd. In contrast, the concentration of metals in plant leaves were seen on the order of Fe>Mn>Cr>Cd>Cu>Pb. As such, Cd showed significantly high concentration in leaves relative to their corresponding dust samples. A high accumulation potential for Fe and Cd was seen from Butea monosperma, while Mn and Pb were accumulated noticeably in Pongamia pinnata and Butea monosperma. Likewise, Cr and Cu were enriched in Calotropis procera, Alstonia scholaris, and Butea monosperma. The overall results of our study suggest that the foliar uptake pattern should vary considerably by an interactive role between plant and metal types.

• 분석과학
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• 제18권1호
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• pp.51-58
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• 2005

A comparison of the analytical data obtained by three $k_0$-NAA software programs was carried out using both the airborne particulate matter collected from an urban site and the certified reference materials of the air filter and urban dust to evaluate the performance of the analysis. The individual $k_0$-NAA standardization methods of three countries, Korea, China and Vietnam which had been modified from the well established $k_0$-program were used for the comparative analysis. The measured concentrations of 30 elements from the two kinds of air samples based on this software were in agreement with each other within about 20% analytical error except for a few elements. By contrast, the results of China and Vietnam were moderately higher than that of Korea due to a systematic error associated with the detection efficiency, gamma peak analysis and geometric effect.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1683-1684
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• 2008

For direct detection of microbes in air, samples have to be collected but environmental particles such as dust are also trapped in such samples. Therefore the isolation of target bacteria from non-biological materials of similar size is of great importance in the identification of such organisms. Dielectrophoresis is an emerging technique that can rapidly separate cells in microfluidics. In this paper we proposed a new method for the separation of airborne microbes using condensation and dielectrophoresis. This system could be used as a continuous flow through separation system for various particles and utilized as a pretreatment technique for microbe detection.